1. Field of the Invention
The present invention relates to a color photographic light-sensitive material containing a novel silver halide emulsion, and a method of developing the same.
2. Description of the Related Art
Various silver halide photographic light-sensitive materials are put into practical use by utilizing the fact that silver halide crystal grains are sensitive to a radiation such as visible light or ultraviolet rays, to form a latent image which is subsequently converted into a visible image by development. Examples of silver halide are silver iodide, silver bromide, silver chloride, and their mixed crystals. In this case, a silver halide to be used is selected in accordance with the application and the required function of a light-sensitive material in which the silver halide is used. For example, silver iodobromide grains having a relatively large grain size are used in a light-sensitive photographic material which is required to have high sensitivity. In contrast, silver iodobromide or silver chlorobromide having a small grain size is used in a duplicating or printing light-sensitive material having relatively low sensitivity. The type of silver halide, the crystal shape, grain size, and the like are all important factors in determining the properties of a given silver halide emulsion. This is described in, for example, "The Theory of the Photographic Process" by T. H. James, 4th. ed., Macmillan Co. Ltd. New York, 1977, "Die Grundlagen der Photographischen Prozesse mit Silverhalogeniden" by C. Hasse, H. Frieser, and E. Klein, Akademische Verlagsgesellschaft, Frankfurt an Main, 1968.
In recent years, the time required for printing and developing photographic materials for prints has been greatly reduced. Therefore, a strong demand has increasingly arisen for a light-sensitive material which has high sensitivity and can be stably processed. Conventionally, a silver chlorobromide emulsion subjected to sulfur sensitization is practically used as a photographic material for prints. However, use of such an emulsion does not permit a reduction in developing time, since development is restrained significantly by the release of bromide ions during the development process. In addition, since these ions gradually accumulate in the processing liquid, variations in the photographic characteristics increase over time. Furthermore, since the silver chlorobromide emulsion has low solubility in water, the fixing time is necessarily long. A high silver chloride emulsion having a high silver chloride content and containing substantially no silver iodide is known as a preferable material for reducing the time required for the development, bleaching, and fixing steps and for minimizing changes in photographic characteristics, as caused by variations in the processing conditions. In a high silver chloride emulsion, cubic grains having a (100) crystal plane are normally formed. However, when these grains are chemically sensitized, they tend to cause fog. Such fog is significant especially when the grains are subjected to gold sensitization. More specifically, fog poses a practical problem in a color developer having high activity for rapid development. Storage fog generated when a light-sensitive material is stored also poses a practical problem. When a high silver chloride emulsion is exposed at high intensity for a short period of time, reciprocity failure is increased. This is another drawback of the high silver chloride emulsion when it is used as a material for prints.
Several methods have been proposed to solve these problems associated with high silver chloride emulsion. Hereinafter, the symbol "JP-A-" will be used to denote a Japanese Patent Disclosure, and the symbol "JP-B-" will be used to designate a Japanese Patent Publication. Further, the symbol "JP-A-(examined)" will be used to specify a published Japanese patent application without having been laid open which was filed before Jan. 1, 1971 when the system of laying open any patent application came into existence. JP-A-48-51627 and JP-A(examined)-49-46932 describe methods in which water-soluble bromide or iodide ions are added after a sensitizing dye is added to a silver halide emulsion, while JP-A-58-108533 and JP-A-60-222845 describe methods in which bromide and silver ions are simultaneously added to silver halide grains having a high silver chloride content, to form layers containing 60 mol % or more of silver bromide on grain surfaces. In a similar method, a layer containing 10 to 50 mol % of silver bromide is formed on part of, or the entire surface of each grain. In still another method proposed, as described in JP-B-50-36978, JP-B-58-24772, U.S. Pat. No. 4,471,050, and West German Patent Application (OLS) No. 3,229,999, bromide ions are added to a silver halide having a high silver chloride content, or else bromide and silver ions are simultaneously added thereto, to perform halide conversion to obtain multilayer grains such as double-structured (i.e., a core and a shell) grains or joint-structured grains. However, these conventional methods do not provide a satisfactory sensitivity level and the like.
One method of chemically sensitizing an emulsion having a high silver chloride content is sulfur sensitization in the presence of a solvent for silver halide, this method being described in JP-A-58-30748. According to another chemical sensitization method, as described in JP-A-58 125612, pAg and/or temperatures during sulfur sensitization are controlled in a two-step manner. However, neither of these methods can provide a sensitivity high enough to permit their end products to be used as photographic light-sensitive materials.
Compounds represented by formulas [I] to [III] presented later are known as antifoggants. U.S. Pat. Nos. 2,394,198 and 2,440,206, for example, disclose the compounds as an antifoggant used when a sulfinic acid compound is used; U.S. Pat. No. 3,047,393 discloses the compounds as an antifoggant for a silver iodobromide; JP-A(examined)-39-25774 discloses that the compounds can be used to stabilize a silver image; JP-A(examined)-42-11305 discloses that the compounds can be used together with a tetraazaindene compound to prevent fog of a silver iodobromide emulsion; JP-A-54-1019 (corresponding to British Patent No. 1,569,758) discloses that the compounds can be used to prevent fog of a silver iodobromide emulsion when an organic thioether compound is used; and JP-A-57-176032 discloses that the compounds can be used together with a cyanine dye and an anti-oxidizing agent to improve latent image fading of a silver iodobromide emulsion. No disclosure, however, has been reported in which the compounds represented by formulas [I] to [III] are applied to a high silver chloride emulsion. In addition, it is very difficult to predict whether or not, or how much the compounds function to prevent fog and to achieve other photographic effects when they are added to a high silver chloride emulsion having a halogen composition different from that of the conventional emulsion.
As is well known, a high silver chloride emulsion is a preferable material for reducing the time required for the developing process. This emulsion can be chemically sensitized to have a sufficient sensitivity. If it is so sensitized, and used in a material for color prints, it will cause fog. The sensitized emulsion has a high-intensity reciprocity failure. Thus, it has been considered to be unadvisable to manufacture a color printing material using a high silver chloride emulsion. It is also known in the art that emulsions will generally cause fog if they are gold-sensitized. Hitherto, no technique has been developed which makes it possible to provide a high silver chloride emulsion that is sensitized greatly enough not to cause an excessive fog even if it has been subjected to gold-plus-sulfur sensitization. It has been demanded that such a technique be developed.